Hyperinflation and its management in COPD

Figures & data

Figure 1 Pressure volume relationship of the passive respiratory system. Lower and upper boundaries of the elastic recoil pressure–volume relationship of the respiratory system in healthy subjects (---), in patients with narrowed airways (—), and in patients with loss of lung elastic recoil (·····). The loops represent tidal breathing at rest (—) and during exercise (·····).

Abbreviations: FRC, functional residual capacity; VC, vital capacity.

Figure 2 Effects of time and resistance on the change in expiratory volume. Rates of changes of volume after a similar given change of alveolar pressure in a subject with normal respiratory system resistance (—) and a resistance 3 times greater (---) such as in COPD, assuming a constant compliance. Note the marked effect of resistance on the volume change, particularly when the available time is shortened.

Abbreviations: COPD, chronic obstructive pulmonary disease.

Figure 3 Iso-volume pressure-flow relationship. Schematic representation of the pressure-flow relationship in a healthy (normal) subject and a patient with COPD, showing the effect of the increased expiratory resistance upon the maximum expiratory flow and in both cases the independence of the maximum flow from the pleural pressure. Copyright © 1986. Modified with permission from Pride NB, Macklem PT. 1986. Lung mechanics in disease. In: Fishman AP (ed). Handbook of physiology, Section 3, Volume III, Part 2: The respiratory system. Bethesda MD: American Physiological Society, pp 659–92.

Abbreviations: COPD, chronic obstructive pulmonary disease.

Figure 4 Maximum and tidal flow-volume curves in subjects with and without flow limitation. In this figure it can be seen an schematic representation of the spontaneous flow-volume curves generated at tidal volume at rest (inner dotted line ····) and peak exercise (dashed line ----) compared with the maximum flow volume curve in a subject without flow limitation able to reduce its end-expiratory lung volume (Panel A) and a flow-limited COPD patient with dynamic hyperinflation (Panel B).

Abbreviations: COPD, chronic obstructive pulmonary disease; IC, inspiratory capacity.

Table 1 Main clinical consequences of dynamic hyperinflation

Exercise limitation and dyspnea

Hypoventilation during exercise

Hypercarbic respiratory failure during exacerbations

Hypercapnia during exercise

Cardiac dysfunction during exercise

Weaning failure

Hypotension and barotraumas during mechanical ventilation

Independent risk factor for survival in COPD subjects

Reduced improvement with exercise training

Figure 5 Tidal volume encroachment by dynamic hyperinflation in COPD. In this figure the effects of respiratory rate and work rate on the end-inspiratory (EILV), end-expiratory lung volume (EELV), tidal volume (ie, EILV–EELV) and minute ventilation in subjects with severe COPD is displayed. While EILV increases with increasing respiratory rate from 20 to 30min⁻¹ (lower left panel), so does EELV resulting in an almost constant (encroached) tidal volume. At respiratory rates higher than 30, though, EILV does not increase any more, however, EELV further increases resulting in a reduced tidal volume and even a drop in ventilation (left upper panel) at respiratory rates higher than 35min⁻¹. In the right lower panel we can see how during progressive exercise tidal volume also decreases at high intensity due again to increase in EELV without parallel increase in EILV (Constructed with data from Puente-Maestu et al 2005).

Abbreviation: COPD, chronic obstructive pulmonary disease; EELV, end-expiratory lung volume; EILV, end-inspiratory lung volume; TLC, total lung capacity.

Table 2 Summary of trials on BD measuring resting or dynamic hyperinflations an outcome

Ref	FEV1 (%)	“n”/design	Intervention	Duration	Resting PFT	Resting hyperinflation	Exercise hyperinflation	Exercise dyspnea	Endurance time CLE	Comment
Single dose
(Belman et al 1996)	40 (3)	13 cross-over against placebo	200μg of salbutamol		Improvement in FEV1 and FVC		Improved	Improved
(Newton et al 2002)	52 (1)//78(1)*	281 TLC>133% and 676 TLC 113%–133%)//retrospective	200μg of salbutamol		~30% improved FEV1	Reduced FRC RV//				TLC was also reduced by BD. overall sensitivity may improve up to ~66% by measuring changes in lung volumes.
(Ramirez-Venegas et al 1997)	52 (13)	16 with positive BD test//cross-over against placebo	50μg of salmeterol		Improvement in FEV1 and FVC	Reduced FRC				lower dyspnea during resistive breathing
(Boni et al 2002)	47 (18)	20//11 with FL	400μg of salbutamol		No changes in FEV1	Improvement in IC only in FL		Improved		Changes in dyspnea correlated with improvements in resting IC
(Di Marco et al 2993)	52 (3)*	20//cross-over against placebo	200μg of salbutamol//12μg of formoterol//50μg of salmeterol//200μg of oxytropium		Improvement in FEV1	Increased IC				Fomoterol better than salmeterol and than oxytropium//Those with decrease IC achieved a larger effect
Long-term
(Celli et al 2003)	43 (12)	40/41//placebo controlled	Tiotropium 18μg/d	4 weeks	Improvement in FEV1, FVC, SVC,	Increased IC and decreased FRC
(O’Donnell et al 2004a)	44 (13)	96/91//placebo controlled	Tiotropium 18μg/d	6 weeks	Improvement VC, but not FEV1,	Increased IC and decreased FRC	Improved	Improved	105 (40)s (21%) >than
(Maltais et al 2005)	43 (13)	131/117//placebo controlled	Tiotropium 18μg/d	6 weeks	Improvement VC, but not FEV1,	Increased IC and decreased FRC	Improved	Improved	171 (58) s> than placebo	Effects seen at 2.5h still at 8h
(O’Donnell2004c)	42 (3)*	23//cross-over against placebo	Salmeterol (50μg bid) added to the daily drug regimen.	2 weeks	Increased FEV1, Improved	Increased IC	Improved	Improved		Increased In peak oxygen uptake and VT at 10w incremental test.
(Man et al 2004)	32 (4)	16 “no reversible”//cross-over against placebo	Salmeterol (50μg bid) added to the daily drug regimen.	2 weeks	No effect on FEV1, FVC, SVC,	Decreased RV/TLC	Improved	Improved	No improvement	Changes in dyspnea correlated with improvements DH and esophageal pressure

Note: Values are men with standard deviation within parenthesis; except *SEM.

Table 3 Subjects likely to benefit for lung volume surgery

Marked disability after rehabilitation (peak work rate <40% predicted)

Quit from smoking at least 6 month before

Understanding of risks and benefits

Heterogeneous enphysiema

Marked hyperinflation

DLCO <50% >20% as percent of predicted

FEV1 < 35% >20% as percent of predicted

Normal ejection fraction

Abbreviations: DL_CO, diffusing capacity of the lung for carbon monoxide; FEV, forced expiratory volume in one second

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